Reticle container

ABSTRACT

A mask container for storing a mask for photolithography, includes a cover and a base having a plurality of tapered corners. The tapered corners taper outward and downward from a top major surface of the base. The cover having the tapered corners extends downward that covers the tapered corners of the base when the cover is attached to the base. The tapered corners of the cover are tapered at about the same angle as the tapered corners of the base so that a surface of the tapered corners of the cover is substantially parallel to a corresponding surface of the tapered corner of the base when the cover is attached to the base. A recess is located in the tapered corners of the cover. A biasing member and a ball-shaped member are located in the tapered corners of the base to mate with the recess when the cover is attached to the base.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and incorporates by referencein its entirety U.S. Provisional Application 62/565,319 filed on Sep.29, 2017.

TECHNICAL FIELD

The disclosure relates to containers having a cover and a base used forstoring and transporting articles, and more particularly tophotolithography mask inner pod covers and bases for transporting andstoring masks or blank substrates.

BACKGROUND

A semiconductor chip patterned using photolithography (for example,extreme ultraviolet photolithography or EUV photolithography using 13.5nm wavelength for patterning) requires a mask or a photo-mask (alsocalled a ‘reticle’) which is contained in a standardized carrier fortransfer to different positions in a clean room or in different cleanrooms for different processes. For example, a blank substrate or a blankis transferred in the standardized carrier using manual or roboticmethods to different locations or clean rooms for cleaning and maskfabrication. The fabricated mask is also transferred inside thestandardized carrier to different locations or clean rooms forphotolithography processes, or storage before or after use. The maskcarrier (also referred to as a mask container, a mask pod, or a maskbox) includes an inner pod and an outer pod. The inner pod contacts theblank substrate or mask, and includes an inner pod cover and an innerpod base or inner pod base plate. The inner pod cover and the inner podbase plate of the inner pod are designed to fit each other with highaccuracy.

In case of positional inaccuracy between the inner pod cover and theinner pod base plate due to environmental factors or the dimensionalinaccuracy of the inner pod base plate and/or the inner pod cover, whenopening or closing the inner pod, there could be contact between innerpod cover and the inner pod base plate. Friction caused by the contactcould generate particles that would fall on the inner pod base plateand/or the mask or blank substrate on the inner pod base plate. Theinner pod cover and the inner pod base plate are commonly made of metalmaterials such as aluminum alloy for weight control. The aluminum matrixis coated with nickel, nickel alloy, chromium, or chromium alloy forenhancing mechanical properties. The friction between the inner podcover and the inner pod base plate would generate particles composed ofthese metals. Particles remaining on the mask could damage the patternson the mask or the blank substrate or block the very small wavelengthEUV radiation causing image errors. Translation, rotation, or rubbingbetween the mask or blank substrate in the inner pod with the particlesmay severely damage the mask or blank substrate. Damaged masks increasethe production cost, increase manufacturing time, and require expensivesystems for checking the defects in the mask. Thus, the avoidance ofparticle generation in an inner pod is desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1(a) shows a plan view of the inner pod or mask container/carrier,according to an embodiment of the present disclosure, and FIG. 1(b)shows a side view of the mask inner pod along a bottom side of the planview of the inner pod of FIG. 1(a).

FIG. 2(a) shows a cross-sectional view of the mask inner pod along a cutline A-A′ in FIG. 1(a) according to an embodiment of the presentdisclosure, and FIG. 2(b) shows a cross-sectional view of the inner podalong the cut line A-A′ in FIG. 1(a) according to another embodiment ofthe present disclosure.

FIGS. 3(a), 3(b), and 3(c) show a process of closing the mask inner podby lowering the inner pod cover toward the inner pod base plateaccording to an embodiment of the present disclosure.

FIGS. 4(a), 4(b), and 4(c) show a process of closing the mask inner podby lowering the inner pod cover toward the inner pod base plateaccording to another embodiment of the present disclosure.

FIGS. 5(a), 5(b), and 5(c) show a process of closing the mask inner podby lowering the inner pod cover toward the inner pod base plateaccording to another embodiment of the present disclosure.

FIG. 6(a) shows the completely closed state of the mask inner pod bylowering the inner pod cover to contact the inner pod base plateaccording to another embodiment of the present disclosure, and FIG. 6(b)shows the completely opened state of the mask inner pod by lifting theinner pod cover away from the inner pod base plate.

FIG. 6(c) shows the completely closed state of the mask inner pod bylowering the inner pod cover to contact the inner pod base plateaccording to an embodiment of the present disclosure, and FIG. 6(d)shows the completely opened state of the mask inner pod by lifting theinner pod cover away from the inner pod base plate.

FIG. 7(a) shows a perspective view of an inner pod cover according to anembodiment of the present disclosure. FIG. 7(b) shows a perspective viewof the corner structure circled in FIG. 7(a). FIG. 7(c) shows aperspective view of lower side the corner structure hidden in FIG. 7(b)and reveals a polymer ball-shaped member and a ball-holding part. FIG.7(d) shows the polymer ball-shaped member and the ball-holding parttaken out from the corner structure in FIG. 7(b).

FIG. 8(a) shows a perspective view of an inner pod cover with fourcorner structures, according to an embodiment of the present disclosure,FIG. 8(b) left figure shows an enlarged view of the bottom structure ofone of the circled corner structure in FIG. 8(a), and FIG. 8(b) rightfigure shows a closed state of the mask inner pod by contacting theinner pod cover and the inner pod base plate.

FIG. 9(a) shows an exploded perspective view of the inner pod cover withthe corner structures and the fasteners separated from the major pieceof the mask inner pod, and FIG. 9(b) shows a perspective view of aninner pod base plate according to an embodiment of the presentdisclosure.

FIG. 10(a) shows a perspective view of the inner pod base plateaccording to an embodiment of the present disclosure, FIG. 10(b) shows acorner structure of the inner pod base plate circled in the inner podbase plate in FIG. 10(a), FIG. 10(c) shows a cross-sectional perspectiveview of the closed mask inner pod with the inner pod cover contactingthe inner pod base plate, and FIG. 10(d) shows a two dimensionalcross-sectional view in FIG. 10(c).

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“being made of” may mean either “comprising” or “consisting of.” In thepresent disclosure, a phrase “one of A, B and C” means “A, B and/or C”(A, B, C, A and B, A and C, B and C, or A, B and C), and does not meanone element from A, one element from B and one element from C, unlessotherwise described.

An embodiment of the disclosure is a mask carrier or EUV mask inner podwithout the problem of particle generation during opening or closing ofthe inner pod cover and the inner pod base plate. The present disclosureprovides a new inner pod designed to reduce contact of the inner podcover and the inner pod base plate and the inner pod base plate, so asto reduce the chance of generating particles due to friction between theinner pod cover and the inner pod base plate, and to improve the closingof the inner pod even when there is positional inaccuracy between theinner pod cover and the inner pod base plate.

FIG. 1(a) shows a plan view of the mask inner pod according to anembodiment of the present disclosure, and FIG. 1(b) shows a side view(not a cross-sectional view) of the mask inner pod, or simply called aninner pod, at a bottom side of the inner pod of FIG. 1(a). The innerpod, including an inner pod cover 10 and an inner pod base plate orinner pod base 20, and a mask or reticle (not shown) is placed on theinner pod base plate 20, thereby protecting the mask stored thereinduring storage and transport. The mask inner pod is further placed in amask outer pod in some embodiments of the present disclosure. In someembodiments of the present disclosure, the mask inner pod is an extremeultraviolet (EUV) mask inner pod for protecting EUV masks or EUV blanksubstrates.

FIG. 1(b) shows a side view of the inner pod along a bottom side of theplan view of the inner pod of FIG. 1(a). The inner pod base plate 20 hasa major area with four cut-corners (not visible in FIG. 1(b)) and thecut-corners are covered by the corner structures of the inner pod cover10, in some embodiments of the present disclosure. In other embodimentsof the present disclosure, the inner pod base plate 20 has a major areawith three or two cut-corners while the other remaining corners are 90degree corners or round corners or a mixture of 90 degree and roundcorners. When there are two corners cut, the two corners are located atopposite positions along a diagonal of the major surface of the innerpod cover 10, in some embodiments of the present disclosure. The sideview in FIG. 1(b) shows that the left and right corners of the inner podcover 10 have corner structures integrally formed with the inner podcover 10 and extending from the top surface level of the inner pod cover10 to the inner pod base plate 20 so as to cover the respective cornersof the inner pod base plate 20. In some embodiments of the presentdisclosure, the corner structure of the inner pod cover 10 has a bottomside higher than a major bottom surface of the inner pod base plate 20(FIG. 1(b)). In other embodiments of the present disclosure, the cornerstructure of the inner pod cover 10 has a bottom side at a samehorizontal level as the major bottom surface of the inner pod base plate20. In some embodiments of the present disclosure, the size of thecorner structures of the inner pod cover 10 is not limited as long as aball-shaped member 30 and a biasing member 40 discussed herein can belocated in the corner structure of the inner pod cover 10. Thecross-sectional shape of the corner structure is an upright trapezoidalshape, in some embodiments of the present disclosure.

The inner pod cover 10 and inner pod base plate 20 are made of nickelcoated aluminum alloy in some embodiments of the present disclosure. Thenickel coating is Ni—P or Ni—Cr in some embodiments of the presentdisclosure. Ni—P or Ni—Cr particles can be generated by friction wherethe inner pod cover 10 and inner pod base plate come into contact. Ifthe friction-generated particles fall on the mask on the inner pod baseplate 20, the particles can cause masking image errors when the mask isused for photolithography.

To prevent the formation of particles generated by friction and toprevent the image error in the nanometer-scaled mask pattern, thepresent disclosure provides a novel configuration of the mask inner pod.

FIG. 2(a) shows a cross-sectional view of the novel mask inner pod alonga cut line A-A′ in FIG. 1(a) according to an embodiment of the presentdisclosure, and FIG. 2(b) shows a cross-sectional view of the mask innerpod along the cut line A-A′ in FIG. 1(a) according to another embodimentof the present disclosure. As shown in FIGS. 2(a) and 2(b), aball-shaped member 30, a biasing member 40 (e.g. an axially biasingmember such as a coil spring, leaf spring, or torsional spring) and arecess (‘dimple’) 50 are provided in the corner (FIG. 1(a)) of the innerpod cover 10 and a cut-corner of the inner pod base plate 20 (dottedlines at corners of FIG. 1(a) indicating the hidden edges of thecut-corners of the inner pod base plate 20 covered by the inner podcover 10). As shown in FIGS. 2(a) and 2(b), the cut-corners of the innerpod base plate 20 are tapered outward and downward from a top majorsurface TS2 of the inner pod base plate 20, forming an incline surfaceor tapered surface S2. The top major surface TS2 of the inner pod baseplate 20 is the surface on which the mask or blank rests. The inner podcover 10 has a plurality of corner structures tapered and extendingdownward and covering the inner pod base plate's 20 tapered cut-cornerswhen the inner pod cover 10 is attached to the inner pod base plate 20,and the tapering of the corner structures of the inner pod cover 10forms upside-down incline surfaces or tapered surfaces S1 between thebottom surface BS1 of the inner pod cover 10 and the surface TS1 of thecorner structure of the inner pod cover 10. The tapered cornerstructures of the inner pod cover 10 are tapered at about the same angleas the inner pod base plate's 20 tapered cut-corners so that inner podcover's 10 corner structure's tapered surface S1 is substantiallyparallel to the corresponding tapered surface S2 of the cut-corner ofthe inner pod base plate 20 when the inner pod cover 10 is attached tothe inner pod base plate 20. The angle of tapering is not limited aslong as the inner pod cover 10 can be combined with the inner pod baseplate 10.

In the embodiment of FIG. 2(a), a ball-shaped member 30 and a biasingmember 40 are located in the inner pod cover's 10 tapered cornerstructure, while the recess or dimple 50 is located on the taperedsurface S2 of the inner pod base plate 20. In the embodiment of FIG.2(b), the ball-shaped member 30 (including a polymer ball) and thespring 40 is located in the inner pod base plate's 20 taperedcut-corners, while the recess or dimple 50 is located on the taperedsurface S1 of the corner structure of the inner pod cover 10. In bothembodiments of FIGS. 2(a) and 2(b), the ball-shaped member 30 mates withthe recess or dimple 50 when the inner pod cover 10 is attached to theinner pod base plate 20.

In some embodiments of the present disclosure, most of the volume (e.g.more than half of the total volume) of the ball-shaped member 30 iseither enclosed in the corner structure of the inner pod cover 10 (e.g.in the embodiment of FIG. 2(a)) or enclosed in the tapered cut-corner ofthe inner pod base plate 20 (e.g. in the embodiment of FIG. 2(b)).

In some embodiments of the present disclosure, the spring 40 is a coilspring (FIGS. 4(a)-4(c)), a leaf spring (FIGS. 2(a) and 2(b) and FIGS.3(a)-3(c)), or a torsional spring (FIGS. 5(a)-5(c)).

In some embodiments of the present disclosure, the ball-shaped member 30is made of an elastic polymer. In some embodiments of the presentdisclosure, the elasticity of the polymer ball is selected to allow theinner pod cover 10 and the inner pod base plate 20 to smoothly slideover each other. In some embodiments of the present disclosure, thepolymer ball-shaped member 30 has a Shore D durometer hardness of about70 to about 90. In some embodiments of the present disclosure, thepolymer is selected from the group consisting of polyether ether ketone(PEEK), polyether ketone (PEK), poly(phenylene sulfide) (PPS),polyphenylsulfone (PPSU), polysulfone (PSU), poly(ethersulfone) (PES),polyetherimide (PEI), polyamide-imide (PAI), and polyetherimide (PEI).

In some embodiments of the present disclosure, the recess or dimple 50is a substantially semi-circular-shaped dimple, as viewed in a crosssection (e.g. FIG. 2(a) or 2(b)). In other embodiments of the presentdisclosure, the recess or dimple 50 can be formed to have other shapesas long as the polymer ball-shaped member is immobilized by mating withit. For example, the recess or dimple 50 may have a triangular shape,pentagon shape, hexagon shape or any shape for mating with the polymerball-shaped member 30.

In FIGS. 3(a)-3(c), 4(a)-4(c), and 5(a)-5(c), the parts of theembodiments are labelled in the same fashion as that in FIGS. 2(a) and2(b). FIGS. 3(a), 3(b), and 3(c) show the processes of combining theinner pod cover 10 and the inner pod base plate 20. As the inner podcover 10 is lowered toward and over the inner pod base plate 20, thetapered corner of the inner pod base 10 contacts the polymer ball-shapedmember 30 and compresses the leaf spring 40. When the polymerball-shaped member 30 reaches the recess or dimple 50, the leaf spring40 pushes the ball-shaped member 30 into the recess or dimple 50,thereby securing the closed state of the mask inner pod. With the innerpod cover 10 securely combined with the inner pod base plate 20, theinner pod cover 10 is prevented from further movement with respect tothe inner pod base plate 20, and the inner pod cover 10 is preventedfrom directly contacting the inner pod base plate 20. Eliminating themovement and direct contact between the inner pod cover 10 and the innerpod base plate 20 prevents friction between the inner pod cover 10 andthe inner pod base plate 20 and prevents the generation of the metalparticles. Thus, particulate contamination of a mask stored in the maskinner pod is reduced, and image error when the mask is used forphotolithography is reduced. In addition, the cost for checking forparticulate defects on the mask stored in the inner pod is reduced.

FIGS. 4(a), 4(b), and 4(c) show processes of combining the inner podcover 10 and the inner pod base plate 20. As the inner pod cover 10 islowered toward and over the inner pod base plate 20, the tapered cornerof the inner pod base 10 contacts the polymer ball-shaped member 30 andcompresses the coil spring 40. When the polymer ball-shaped member 30reaches the recess or dimple 50, the coil spring 40 pushes theball-shaped member 30 into the recess or dimple 50, thereby securing theclosed state of the mask inner pod. With the inner pod cover 10 securelycombined with the inner pod base plate 20, the inner pod cover 10 isprevented from further movement with respect to the inner pod base plate20. Eliminating the movement and direct contact between the inner podcover 10 and the inner pod base plate 20 prevents friction between theinner pod cover 10 and the inner pod base plate 20 and prevents thegeneration of the metal particles. Thus, particulate contamination of amask stored in the mask inner pod is reduced, thereby preventing imageerror when the mask is used for photolithography. In addition, the costfor checking for particulate defects on the mask stored in the inner podis reduced.

FIGS. 5(a), 5(b), and 5(c) show processes of combining the inner podcover 10 and the inner pod base plate 20. As the inner pod cover 10 islowered toward and over the inner pod base plate 20, the tapered cornerof the inner pod base 10 contacts the polymer ball-shaped member 30 andcompresses the torsional spring 40. When the polymer ball-shaped member30 reaches the recess or dimple 50, the torsional spring 40 pushes theball-shaped member 30 into the recess or dimple 50, thereby securing theclosed state of the mask inner pod. With the inner pod cover 10 securelycombined with the inner pod base plate 20, the inner pod cover 10 isprevented from further movement with respect to the inner pod base plate20, and the inner pod cover 10 is prevented from directly contacting theinner pod base plate 20. Eliminating the movement and direct contactbetween the inner pod cover 10 and the inner pod base plate 20 preventsfriction between the inner pod cover 10 and the inner pod base plate 20and prevents the generation of the metal particles. Thus, particulatecontamination of a mask stored in the mask inner pod is reduced, therebypreventing image error when the mask is used for photolithography. Inaddition, the cost for checking for particulate defects on the maskstored in the inner pod is reduced.

FIG. 6(a) shows the dimensions of the completely closed state of themask inner pod of FIG. 2(b). The closed mask inner pod includes theinner pod cover 10 and the inner pod base plate 20 contacting eachother. The inner pod cover 10 includes a top horizontal plate parthaving a bottom surface. The bottom surface at the central area of thetop horizontal plate part of the mask inner pod cover 10, is spacedapart from the top major surface TS2 of the inner pod base plate 20 toprovide space for storing the mask or blank contacting the top majorsurface TS2 of the inner pod base plate 20, in some embodiments of thepresent disclosure. In some embodiments of the present disclosure, themask is placed at the central region of the top major surface TS2 of theinner pod base plate 20, and is not contacted by the inner pod cover 10.

As shown in FIG. 6(a), the polymer ball-shaped member 30 has a diameterof about 2 to 5 mm, in some embodiments of the present disclosure. Theseparation between the tapered surface S2 of the cut-corner of the innerpod base plate 20 and the tapered surface S1 of the corner structure ofthe inner pod cover 10 is between about 0 and 4 mm. The height from ahorizontal plane of the major bottom surface BS2 of the inner pod baseplate 20 to the center of the polymer ball-shaped member 30 is about 2to 7 mm. In the completely closed state, the contact between the polymerball-shaped member 30 and the leaf spring 40 is maintained so that theleaf spring 40 applies compressive force to push the polymer ball-shapedmember 30 into the recess or dimple 50 which has depth of about 1 to 2mm in some embodiments of the present disclosure.

FIG. 6(b) shows the opened state of the inner pod with the inner podcover 10 disconnected from the inner pod base plate 20. The contactbetween the polymer ball-shaped member 30 and the leaf spring 40 ismaintained, although the compressive force generated by the leaf spring40 to push the polymer ball-shaped member 30 can be smaller compared tothe closed state in FIG. 6(a). In some embodiments of the presentdisclosure, more than half the volume of the polymer ball-shaped member30 is embedded in the tapered cut-corner of the inner pod base plate 20.

In FIG. 6(b), the inner pod cover 10 has a tapered surface S1 of acorner structure including a recess or dimple 50 that can cover asurface of the polymer ball-shaped member 30. An acute corner with anacute angle α between the tapered surface S2 of the inner pod base plate20 and the bottom surface BS2 of the inner pod base plate 20 is cut(FIG. 6(b)) so that a horizontal plane of the bottom edge BE2 of thetapered surface S2 of the cut-corner of the inner pod base plate 20 is avertical distance V_(BE2) of about 1 to 2 mm above a horizontal plane ofthe bottom surface BS2 of the inner pod base plate 20. Also, a verticalplane of the bottom edge BE2 of the inner pod base plate 20 is ahorizontal distance H_(BE2) of about 1 to 2 mm farther from a verticalplane of an adjacent edge of the bottom surface BS2 of the inner podbase plate 20.

Also, a top obtuse corner with an obtuse angle β between the top majorsurface TS2 and the tapered surface S2 of the cut-corner of the innerpod base plate 20 is cut (FIG. 6(b)) so that a horizontal plane of thetop edge TE2 of the tapered surface of the cut-corner of the inner podbase plate 20 is a vertical distance V_(TE2) of about 1 to 2 mm below ahorizontal plane of the top major surface TS2 of the inner pod baseplate 20, and a vertical plane of the top edge TE2 of the taperedsurface S2 of the cut-corner of the inner pod base plate 20 is ahorizontal distance of H_(TE2) of about 1 to 2 mm farther from avertical plane of the adjacent edge of the top major surface TS2 of theinner pod base plate 20.

Similarly, the obtuse corner with the angle β between a bottom edge BE1of the tapered surface S1 of the corner structure of the inner pod cover10 and a bottom surface BS1 of the corner structure of the inner podcover 10 is cut so that a horizontal plane of the bottom edge BE1 of thetapered surface S1 of the corner structure of the inner pod cover 10 isa vertical distance V_(BE1) of about 1 to 2 mm above a horizontal planeof the bottom surface BS1 of the corner structure of the inner pod cover10, and a vertical plane of the bottom edge BE1 of the tapered surfaceS1 is a horizontal distance H_(BE1) of about 1 to 2 mm farther from avertical plane of the adjacent edge of the bottom major surface BS1 ofthe inner pod cover 10. The removal of the acute and obtuse corners ofthe inner pod base plate 20 and the inner pod cover 10 in FIGS. 6(a) and6(b) is designed to further avoid the contact and friction between theinner pod cover 10 and the inner pod base plate 20.

FIG. 6(c) shows the dimensions of the completely closed state of themask inner pod of FIG. 2(a). The closed mask inner pod includes theinner pod cover 10 and the inner pod base plate 20 contacting eachother. The inner pod cover 10 includes a top horizontal plate parthaving a bottom surface. The bottom surface at the central area of thetop horizontal plate part of the mask inner pod cover 10, is spacedapart from the top major surface TS2 of the inner pod base plate 20 toprovide space for storing the mask or blank contacting the top majorsurface TS2 of the inner pod base plate 20, in some embodiments of thepresent disclosure. In some embodiments of the present disclosure, themask is placed at the central region of the top major surface TS2 of theinner pod base plate 20, and is not contacted by the inner pod cover 10.As shown in FIG. 6(c), the polymer ball-shaped member 30 has a diameterof about 2 to 5 mm, in some embodiments of the present disclosure. Theseparation between the tapered surface S2 of the cut-corner of the innerpod base plate 20 and the tapered surface S1 of the corner structure ofthe inner pod cover 10 is between about 0 and 4 mm. The height from ahorizontal plane of the major bottom surface BS2 of the inner pod baseplate 20 to the center of the polymer ball-shaped member 30 is about 2to 7 mm. In the completely closed state, the contact between the polymerball-shaped member 30 and the leaf spring 40 is maintained so that theleaf spring 40 applies compressive force to push the polymer ball-shapedmember 30 into the recess or dimple 50 which has depth of about 1 to 2mm in some embodiments of the present disclosure.

FIG. 6(d) shows the opened state of the inner pod with the inner podcover 10 disconnected from the inner pod base plate 20. The contactbetween the polymer ball-shaped member 30 and the leaf spring 40 ismaintained, although the compressive force generated by the leaf spring40 to push the polymer ball-shaped member 30 can be smaller compared tothe closed state in FIG. 6(c). In some embodiments of the presentdisclosure, more than half the volume of the polymer ball-shaped member30 is embedded in the corner structure of the inner pod cover 10.

In FIG. 6(d), the inner pod base plate 20 has a tapered surface S2 of acut-corner including a recess or dimple 50 that can cover a surface ofthe polymer ball-shaped member 30 and the coverage is not limited. Theacute corner having angle α between the tapered surface S2 of the innerpod base plate 20 and the bottom surface BS2 of the inner pod base plate20 is cut (FIG. 6(d)) so that a horizontal plane of the bottom edge BE2of the tapered surface S2 of the cut-corner of the inner pod base plate20 is a vertical distance V_(BE2) of about 1 to 2 mm above a horizontalplane of the bottom surface BS2 of the inner pod base plate 20. Also, avertical plane of the bottom edge BE2 of the inner pod base plate 20 isa horizontal distance H_(BE2) of about 1 to 2 mm farther from a verticalplane of an adjacent edge of the bottom surface BS2 of the inner podbase plate 20.

Also, the top obtuse corner having an angle β between the top majorsurface TS2 and the tapered surface S2 of the cut-corner of the innerpod base plate 20 is cut (FIG. 6(d)) so that a horizontal plane of thetop edge TE2 of the tapered surface S2 of the cut-corner of the innerpod base plate 20 is a vertical distance V_(TE2) of about 1 to 2 mmbelow a horizontal plane of the top major surface TS2 of the inner podbase plate 20, and a vertical plane of the top edge TE2 of the taperedsurface S2 of the cut-corner of the inner pod base plate 20 is ahorizontal distance H_(TE2) of about 1 to 2 mm farther from a verticalplane of an adjacent edge of the top major surface TS2 of the inner podbase plate 20.

Similarly, the obtuse corner having an angle β between the taperedsurface S1 of the corner structure of the inner pod cover 10 and abottom surface BS1 of the corner structure of the inner pod cover 10 iscut so that a horizontal plane of the bottom edge BE1 of the taperedsurface S1 of the corner structure of the inner pod cover 10 is avertical distance V_(BE1) of about 1 to 2 mm above a horizontal plane ofthe bottom surface BS1 of the corner structure of the inner pod cover10, and a vertical plane of the bottom edge BE1 of the tapered surfaceS1 is a horizontal distance H_(BE1) of about 1 to 2 mm farther from avertical plane of the adjacent edge of the bottom major surface BS1 ofthe inner pod cover 10. The removal of the acute and obtuse corners ofthe inner pod base plate 20 and the inner pod cover 10 in FIGS. 6(c) and6(d) is designed to further avoid the contact and friction between theinner pod cover 10 and the inner pod base plate 20.

FIG. 7(a) shows a perspective view of the inner pod cover 10 includingcorner structures 60 and fasteners 70 fixing the corner structures 60 tothe inner pod cover 10. FIG. 7(b) shows a detailed view of the circledregion in FIG. 7(a), FIG. 7(c) shows a bottom view of the cornerstructure 60. FIG. 7(d) shows a detailed view of the circled region inFIG. 7(c). In some embodiments, the inner pod cover is an EUV inner podcover (or EIP cover).

In FIG. 7(a), each of the corner structures 60 has two fasteners 70 tofix the corner structure 60 in the inner pod cover 10 to prevent anymovement of the inner pod cover 10 when the inner pod cover 10 contactsthe inner pod base plate 20 in the completely closed state. In otherembodiments of the present disclosure, any number of fasteners 70 isallowed as long as the corner structure 60 is securely fixed in theinner pod cover 10. The fasteners 70 can be threaded screws made ofpolymer material or metal such as stainless steel, carbon steel, andtitanium alloy materials. In some embodiments of the present disclosure,the fasteners 70 are used to form non-permanent joint. In otherembodiments of the present disclosure, the fasteners 70 are used to formpermanent joint, and can be threadless screws, needles, or a solderweld.

The corner structure 60 is formed of any suitable material, including anickel coated Al alloy or a high performance plastic, in someembodiments of the present disclosure. The high performance plasticincludes PEK, PEEK, PPS, PA, PPSU, PSU, and PES. The corner structure 60is attached to the inner pod cover 10 by fasteners 70. In someembodiments of the present disclosure, the polymer ball-shaped member 30and the biasing member 40 are contained in an enclosure or ball-holdingpart 80, which is inserted into a hole provided in the tapered surfaceof the corner structure 60. In some embodiments of the presentdisclosure, the enclosure or ball-holding part 80 is made of a highperformance plastic. The corner structure 60 is made of the samematerial as the inner pod cover 10, in some embodiments of the presentdisclosure. In other embodiments of the present disclosure, the cornerstructure 60 is made of a material different from the inner pod cover10. The corner structure 60 has a rounded outer surface, in someembodiments of the present disclosure. In other embodiments of thepresent disclosure, the corner structure 60 has a 90 degree corner,depending on the requirement of the inner pod during manual or roboticmanipulation in the lithographic processes.

In FIG. 7(c), the polymer ball-shaped member 30 protrudes from thetapered surface of the corner structure 60 of the inner pod cover 10.FIG. 7(d) is a detailed view of the circled region in FIG. 7(c). Asshown in FIG. 7(d), the ball-holding part 80 surrounding and holding thepolymer ball-shaped member 30 has a cylindrical shape with thelarger-diameter top portion having a hole from which the polymerball-shaped member 30 protrudes, and the portion below thelarger-diameter top portion has a smaller diameter. The region betweenthe larger-diameter portion and the smaller-diameter portion has anindentation facilitated for the ball-holding part 80 to fix into thecorner structure 60 which has a tiny protrusion (not shown) inside thehole to mate with the indentation of the ball-holding part 80 so as tosecure the ball-holding part 80 in the corner structure 60 in someembodiments of the present disclosure.

FIGS. 8(a), 8(b), 9(a), and 9(b) show the structures of the inner podcover 10 and inner pod base plate 20 according to an embodiment of thepresent disclosure. In the embodiment shown in FIG. 8(a), the inner podcover 10 has four corner structures 60. In FIG. 8(b) the cornerstructure 60 is drawn to be transparent with outlines indicating thatthe corner structure 60 has a top protrusion TP and bottom protrusionBP, with the top protrusion TP inserted into a top space provided by theinner pod cover 10 while the bottom protrusion BP is inserted into ahole formed in the inner pod cover 10 so as to secure the cornerstructure 60 with the inner pod cover 60 when the fasteners 70 areinserted into the aligned holes (not shown) provided in the topprotrusion TP and the bottom protrusion BP of the corner structure 60and provided in the portion of the inner pod cover 10 between the topand the bottom protrusions TP and BP of the corner structure 60. Theleft figure of FIG. 8(b) shows that the ball-holding part 80 penetratesinto the corner structure 60. The right figure of FIG. 8(b) shows abottom perspective view of the corner structure 60 and the inner podbase plate 20 which is drawn to be transparent with outlines to indicatethe shape of the inner pod base plate 20. The right figure of FIG. 8(b)shows that the polymer ball-shaped member 30 is fitted into the recessor dimple 50 of the inner pod base plate 20.

FIG. 9(a) shows an exploded perspective view of an inner pod cover 10according to an embodiment of the present disclosure. FIG. 9(a) showsthe structure of the inner pod cover 10 described in FIGS. 8(a) and8(b). FIG. 9(b) shows that the inner pod base plate 20 further includesalignment members or guides 90 fixed to the corners of the inner podbase plate 20. The alignment members or guides 90 have a shapeprotruding into the space in the central region of the inner pod cover10 so as to maintain an open space provided at the central region of theinner pod cover 10 at the central region of the inner pod base plate 20for the mask or blank. Further, the alignment members or guides 90secure the mask placed onto the top major surface of the inner pod baseplate 20 so that the mask does not move during transfer and generateparticles by friction. The alignment member 90 is made of a polymermaterial including the above-listed polymer materials used to make thepolymer ball-shaped member 30 in some embodiments of the presentdisclosure. As shown in FIG. 9(b), the alignment member 90 is a beamshape protrusion protruding from the top major surface TS2 of the innerpod base plate 20, in some embodiments of the present disclosure. Inother embodiments of the present disclosure, the shape of the alignmentmember 90 can be any shape including a triangular shape as long as thepurpose of alignment between the space provided by the central region ofthe inner pod cover 20 and the central region of the inner pod baseplate 20 is achieved. Also, FIG. 9(b) shows that the alignment members90 have two vertical protrusions 91 and 92 formed at both opposite endsof the alignment members 90, in some embodiments of the presentapplication. In other embodiments of the present disclosure, thealignment member 90 has a one-piece protrusion formed from one end toanother opposite end of the alignment member 90.

Although the inner pod cover 10 and the inner pod base plate 20 areshown as having a substantially rectangular shape in the exemplaryembodiments, other shapes of the inner pod cover 10 and the inner podbase plate 20 are within the scope of the present disclosure. The innerpod cover 10 and the inner pod base plate 20 can be other polygonalshapes including triangular, hexagonal, and octagonal, or substantiallycurved shapes including semi-circular, circular, and oval. Thesubstantially curved shapes can further include tapered shapes like thetapered surfaces of the cut-corners of the inner pod base plate 20 orthe tapered surface of the corner structure of the inner pod cover 10.

FIGS. 10(a), 10(b), 10(c), and 10(d) illustrate detailed views of thetapered corner regions of the inner pod cover 10 and the inner baseplate 20, according to an embodiment of the present disclosure. Theinner pod base plate 20 shown in FIG. 10(a) has additional (not labeled)indentations formed on the major surface TS2 for the purpose of reducingthe contact between the inner pod cover 10 and the inner pod base plate20 and/or the mask stored therein. Also, the inner pod base plate 20shown in FIG. 10(a) optionally includes a polymer film fixed onto thetop major surface TS2 of the inner pod base plate 20 to reduce thecontact between the inner pod cover 10 and the inner pod base plate 20.

FIG. 10(b) shows an enlarged view of the tapered corner showing acircular-shaped recess or dimple 50, in some embodiments of the presentdisclosure. The recess or dimple 50 can be any shape includingtriangular shape, rectangular shape, pentagon shape, hexagon shape, orany shape as long as the ball-shaped member 30 can be immobilized bymating with it. The recess or dimple 50 can be formed on the inclinetapered surface of the cut-corner of the inner pod base plate 20 or canbe another component that is implemented to the inner pod base plate 20by other methods such as using adhesive or welding method.

FIG. 10(c) shows a cross-sectional perspective view of the corner regionshowing the top protrusion TP and the bottom protrusion BP of the cornerstructure 60 inserted into two spaces provided in the inner pod cover10. As shown in FIG. 10(c), the top protrusion TP has a longerhorizontal length than the bottom protrusion BP, in some embodiments ofthe present disclosure. The longer top protrusion TP allows the fastener70 to pass through so as to fix the corner structure 60 to the inner podcover 10. The shorter bottom protrusion BP of the corner structure 60penetrates into a space or hole provided by the inner pod cover 10 so asto fix the position of the corner structure 60 with respect to the innerpod cover 10. In the embodiment shown in FIG. 10(c), the shorter bottomprotrusion BP of the corner structure 60 does not allow the fastener 70to pass through. In another embodiment of the present disclosure, thebottom protrusion BP of the corner structure 60 has a same horizontallength as the top protrusion TP of the corner structure 60 so as toallow the fastener 70 to pass through. In further embodiments of thepresent disclosure, the bottom protrusion BP of the corner structure 60has a longer horizontal length than the top protrusion TP so as toprevent the motion or any possibility of dislocation of the cornerstructure 60 with respect to the inner pod cover 10.

The ball-holding part 80 and the polymer ball-shaped member 30 areinserted into the space provided in the corner structure 60 of the innerpod cover 10. The inner pod cover 10 has an upper structure designed forassembly with the mask outer pod for robust transportation of the maskinside the mask inner pod cover 10. FIG. 10(d) is a two-dimensionalcross-sectional view showing the inner pod base plate 20 has an optionalspace provided at the edge so that a horizontal plane of the bottomsurface BS3 of the edge of the inner pod base plate 20 is above ahorizontal plane of the major bottom surface BS2 of the inner pod baseplate 20.

The mask inner pod presented in the present disclosure is not limited tomasks, and the inner pod can be used as a container for any componentsuch as electronic components or electromechanical components such asthin film induction components, electronic memories, solid state drivesetc.

An embodiment according to the present disclosure includes a containerfor storing an article. The container includes a base having a pluralityof tapered corners. The tapered corners taper outward and downward froma top major surface of the base. The container also includes a coverhaving a plurality of tapered corners extending downward that cover thetapered corners of the base when the cover is attached to the base. Thetapered corners of the cover are tapered at about the same angle as thetapered corners of the base so that a surface of the tapered corners ofthe cover is substantially parallel to a corresponding surface of thetapered corner of the base when the cover is attached to the base. Thecontainer also includes a biasing member and a ball-shaped memberlocated in the tapered corners of the base, and a recess located in thetapered corners of the cover. The ball-shaped member mates with therecess when the cover is attached to the base. In some embodiments ofthe present disclosure, the biasing member of the container includes anaxially biasing member. In some embodiments of the present disclosure,the axially biasing member includes one of a coil spring, a leaf spring,and a torsion spring. In some embodiments of the present disclosure, theball-shaped member is in contact with the biasing member, and theball-shaped member is made of a polymer. In some embodiments of thepresent disclosure, the container is made of a polymer selected from thegroup consisting of polyether ether ketone (PEEK), polyether ketone(PEK), poly(phenylene sulfide) (PPS), polyphenylsulfone (PPSU),polysulfone (PSU), poly(ethersulfone) (PES), polyetherimide (PEI),polyamide-imide (PAI), and polyetherimide (PEI). In some embodiments ofthe present disclosure, the ball-shaped member has a Shore D durometerhardness of about 70 to about 90. In some embodiments of the presentdisclosure, the ball-shaped member and the biasing member are containedin an enclosure and the enclosure is made of a polymer. In someembodiments of the present disclosure, the cover contacts the base onlythrough contacting the tapered corners of the cover and the taperedcorners of the base. In some embodiments of the present disclosure, thecover contacts the base only through contacting the biasing member andthe recess. In some embodiments of the present disclosure, the taperedcorners of the cover are formed integrally with the cover. The basefurther includes alignment members. Each of the alignment members hasvertical protrusions located at opposite ends of the alignment members.The alignment members are formed of polymer. In some embodiments of thepresent disclosure, the base has four tapered corners. In someembodiments of the present disclosure, the base has a space provided atan edge of the base so that a horizontal plane of the edge is above ahorizontal plane of a major bottom surface of the base. In someembodiments of the present disclosure, the container is an inner pod foran extreme ultraviolet (EUV) mask, the cover is an inner pod cover, andthe base is an inner pod base.

Another embodiment according to the present disclosure includes acontainer for storing an article. The container includes a base having aplurality of tapered corners. The tapered corners taper outward anddownward from a top major surface of the base. The container alsoincludes a cover having a plurality of integrated tapered cornersextending downward that cover the tapered corners of the base when thecover is attached to the base. The tapered corners of the cover aretapered at about the same angle as the tapered corners of the base sothat a surface of the tapered corners of the cover is substantiallyparallel to a corresponding surface of the tapered corner of the basewhen the cover is attached to the base. The container also includes abiasing member and a ball-shaped member located in the tapered cornersof the cover, and a recess located in the tapered corners of the base.The ball-shaped member mates with the recess when the cover is attachedto the base. In some embodiments of the present disclosure, the biasingmember of the container includes an axially biasing member. The axiallybiasing member includes one of a coil spring, a leaf spring, and atorsion spring. The ball-shaped member is in contact with the biasingmember, and the ball-shaped member is made of a polymer. In someembodiments of the present disclosure, the container is made of apolymer selected from the group consisting of polyether ether ketone(PEEK), polyether ketone (PEK), poly(phenylene sulfide) (PPS),polyphenylsulfone (PPSU), polysulfone (PSU), poly(ethersulfone) (PES),polyetherimide (PEI), polyamide-imide (PAI), and polyetherimide (PEI).The ball-shaped member has a Shore D durometer hardness of about 70 toabout 90. In some embodiments of the present disclosure, the ball-shapedmember and the biasing member are contained in an enclosure and theenclosure is made of a polymer. In some embodiments of the presentdisclosure, the cover contacts the base only through contacting thetapered corners of the cover and the tapered corners of the base. Insome embodiments of the present disclosure, the cover contacts the baseonly through contacting the biasing member and the recess. In someembodiments of the present disclosure, the tapered corners of the coverare formed integrally with the cover. The base further includesalignment members. Each of the alignment members has verticalprotrusions located at opposite ends of the alignment members. Thealignment members are formed of polymer. In some embodiments of thepresent disclosure, the base has four tapered corners. In someembodiments of the present disclosure, the base has a space provided atan edge of the base so that a horizontal plane of the edge is above ahorizontal plane of a major bottom surface of the base. In someembodiments of the present disclosure, the container is an inner pod foran extreme ultraviolet (EUV) mask, the cover is an inner pod cover, andthe base is an inner pod base.

Another embodiment according to the present disclosure is a containerfor storing an article. The container includes a base having a pluralityof tapered corners. The tapered corners taper outward and downward froma top major surface of the base. The container also includes a coverhaving a plurality of detachable tapered corners extending downward thatcover the tapered corners of the base when the cover is attached to thebase. The tapered corners of the cover are tapered at about the sameangle as the tapered corners of the base so that a surface of thetapered corners of the cover is substantially parallel to acorresponding surface of the tapered corner of the base when the coveris attached to the base. The container also includes a biasing memberand a ball-shaped member located in the tapered corners of the cover,and a recess located in the tapered corners of the base. The ball-shapedmember mates with the recess when the cover is attached to the base. Insome embodiments of the present disclosure, the biasing member of thecontainer includes an axially biasing member. The axially biasing memberincludes one of a coil spring, a leaf spring, and a torsion spring. Theball-shaped member is in contact with the biasing member, and theball-shaped member is made of a polymer. In some embodiments of thepresent disclosure, the container is made of a polymer selected from thegroup consisting of polyether ether ketone (PEEK), polyether ketone(PEK), poly(phenylene sulfide) (PPS), polyphenylsulfone (PPSU),polysulfone (PSU), poly(ethersulfone) (PES), polyetherimide (PEI),polyamide-imide (PAI), and polyetherimide (PEI). The ball-shaped memberhas a Shore D durometer hardness of about 70 to about 90. In someembodiments of the present disclosure, the ball-shaped member and thebiasing member are contained in an enclosure and the enclosure is madeof a polymer. In some embodiments of the present disclosure, the covercontacts the base only through contacting the tapered corners of thecover and the tapered corners of the base. In some embodiments of thepresent disclosure, the cover contacts the base only through contactingthe biasing member and the recess. In some embodiments of the presentdisclosure, the tapered corners of the cover are formed integrally withthe cover. The base further includes alignment members. Each of thealignment members has vertical protrusions located at opposite ends ofthe alignment members. The alignment members are formed of polymer. Insome embodiments of the present disclosure, the base has four taperedcorners. In some embodiments of the present disclosure, the base has aspace provided at an edge of the base so that a horizontal plane of theedge is above a horizontal plane of a major bottom surface of the base.In some embodiments of the present disclosure, the container is an innerpod for an extreme ultraviolet (EUV) mask, the cover is an inner podcover, and the base is an inner pod base.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A mask container for storing a mask forphotolithography, comprising: a base having a plurality of taperedcorners, wherein the tapered corners taper outward and downward from atop major surface of the base; a cover having a plurality of taperedcorners extending downward that cover the tapered corners of the basewhen the cover is attached to the base, wherein the tapered corners ofthe cover are tapered at about the same angle as the tapered corners ofthe base so that a surface of the tapered corners of the cover issubstantially parallel to a corresponding surface of the tapered cornerof the base when the cover is attached to the base; a biasing member anda ball-shaped member located in the tapered corners of the base; and arecess located in the tapered corners of the cover, wherein theball-shaped member mates with the recess when the cover is attached tothe base.
 2. The mask container according to claim 1, wherein thebiasing member includes an axially biasing member.
 3. The mask containeraccording to claim 2, wherein the axially biasing member includes one ofa coil spring, a leaf spring, and a torsion spring.
 4. The maskcontainer according to claim 1, wherein the ball-shaped member is incontact with the biasing member.
 5. The mask container according toclaim 4, wherein the ball-shaped member is made of a polymer.
 6. Themask container according to claim 5, wherein the polymer is selectedfrom the group consisting of polyether ether ketone (PEEK), polyetherketone (PEK), poly(phenylene sulfide) (PPS), polyphenylsulfone (PPSU),polysulfone (PSU), poly(ethersulfone) (PES), polyetherimide (PEI),polyamide-imide (PAI), and polyetherimide (PEI).
 7. The mask containeraccording to claim 4, wherein the ball-shaped member has a Shore Ddurometer hardness of about 70 to about
 90. 8. The mask containeraccording to claim 4, wherein the ball-shaped member and the biasingmember are contained in an enclosure.
 9. The mask container according toclaim 8, wherein the enclosure is made of a polymer.
 10. The maskcontainer according to claim 1, wherein the cover contacts the base onlythrough contacting the tapered corners of the cover and the taperedcorners of the base.
 11. The mask container according to claim 1,wherein the cover contacts the base only through contacting the biasingmember and the recess.
 12. The mask container according to claim 1,wherein the tapered corners of the cover are formed integrally with thecover.
 13. The mask container according to claim 1, wherein the basefurther includes alignment members.
 14. The mask container according toclaim 13, wherein each of the alignment members has vertical protrusionslocated at opposite ends of the alignment members.
 15. The maskcontainer according to claim 13, wherein the alignment members areformed of a polymer.
 16. The mask container according to claim 1,wherein the base has four tapered corners.
 17. The mask containeraccording to claim 1, wherein the base has a space provided at an edgeof the base so that a horizontal plane of the edge is above a horizontalplane of a major bottom surface of the base.
 18. The mask containeraccording to claim 1, wherein the container is an inner pod for anextreme ultraviolet (EUV) mask, the cover is an inner pod cover, and thebase is an inner pod base.
 19. A mask container for storing a mask forphotolithography, comprising: a base having a plurality of taperedcorners, wherein the tapered corners taper outward and downward from atop major surface of the base; a cover having a plurality of integratedtapered corners extending downward that cover the tapered corners of thebase when the cover is attached to the base, wherein the tapered cornersof the cover are tapered at about the same angle as the tapered cornersof the base so that a surface of the tapered corners of the cover issubstantially parallel to a corresponding surface of the tapered cornerof the base when the cover is attached to the base; a biasing member anda ball-shaped member located in the tapered corners of the cover; and arecess located in the tapered corners of the base, wherein theball-shaped member mates with the recess when the cover is attached tothe base.
 20. A mask container for storing a mask for photolithography,comprising: a base having a plurality of tapered corners, wherein thetapered corners taper outward and downward from a top major surface ofthe base; a cover having a plurality of detachable tapered cornersextending downward that cover the tapered corners of the base when thecover is attached to the base, wherein the tapered corners of the coverare tapered at about the same angle as the tapered corners of the baseso that a surface of the tapered corners of the cover is substantiallyparallel to a corresponding surface of the tapered corner of the basewhen the cover is attached to the base; a biasing member and aball-shaped member located in the tapered corners of the cover; and arecess located in the tapered corners of the base, wherein theball-shaped member mates with the recess when the cover is attached tothe base.